Inheritance of Traits Introduction to Mendelian Genetics A

Inheritance of Traits Introduction to Mendelian Genetics

A Brief History In the past, people did not understand how traits were inherited, but there were many guesses based on things that could be observed. Two theories emerged…. Blending Theory - offspring are a straight mix. Particulate Theory - traits are inherited as "particles", offspring receive a "piece" from each parent, some pieces may hide the others. Golden Doodle

Who was Gregor Mendel? He was known as the “FATHER OF GENETICS” He discovered how traits were inherited. GENETICS – study of heredity HEREDITY – the passing of traits from parents to offspring

Mendel’s Peas Mendel did his study on pea plants which are easy to cross and have many traits. tall/short purple /white flowers smooth/wrinkled seed

Pea plants can easily be self-fertilized or cross-fertilized

True-Breeding Plants -always create plants that look like themselves (purple or white flowers) Hybrids – offspring of two different true breeding plants (Purple x White = Hybrid)

Principle of Dominance & Recessiveness Some traits are dominant over others. - Tall parent x Short parent = all tall hybrids *Tall, purple, and smooth are dominant traits (always observed if present) * Short, white, and wrinkled are recessive traits (hidden in presence of a dominant trait)

Mendel discovered that each trait is controlled by variations of genes (allele) Genes – segment of DNA that determine your traits Genes are located on chromosomes

Homologous Chromosomes & Alleles Organisms have sets of chromosomes with each chromosome having a unique set of genes. Many organisms have two copies of each chromosome, one from each parent. Chromosomes that have the same genes are called homologous chromosomes because they have the same genes (homo=same, logos – relation). They may have the same genes, but can have different versions of those genes, called alleles.

Principle of Segregation When a parent makes sperm or eggs, their homologous chromosomes separate so that each sperm or egg cell has only one of the two possible alleles. The gametes (egg or sperm) contain only one of the two possible chromosomes. Question: Why is it necessary to donate only one copy of each chromosome to the child when humans normally have 2 copies?

Quick Check - What do we know so far? 1. The “Father of Genetics” is ______ 2. Genetics is the study of _______, which is how traits are passed from _____ to ______ 3. Mendel studied what organism? ______ 4. If one trait covers up another one, we say that it is _______, the one that is covered up is ______ 5. A “true-breeding” plant is one that can only produce plants like itself a) true b) false 6. If a tall and a short plant are crossed, it will create a a) zygote b) gene c) hybrid

Mendel’s Experiments

Mendel’s Crosses Explained T is the allele for tall (dominant) T is the allele for short (recessive) Y is the allele for smooth (dominant) y is the allele for wrinkled (recessive)

GENOTYPE - the pair of alleles an organism has for a gene (TT, Tt, tt) PHENOTYPE - the observable trait determined by the genotype

Check for understanding 1. The passing of traits from parents to offspring is known as __________ 2. Who was the father of genetics? _____ 3. Genes are located on ________ 4. Every gene is made of two a. genotypes b. alleles c. cells 5. The organism’s outward appearance, such as wrinkled seeds are referred to as the a) phenotype b) genotype

6. The letters (ex. RR) that represent the traits are referred to as the a) phenotype b) genotype 7. An organism that has two different alleles, or letters, such as Rr is: a) homozygous b) heterozygous 8. 7. An organism that has two of the same alleles, or letters, such as RR is: a) homozygous b) heterozygous 9. Which of the following sets would represent Mendel’s Parent (P) generation? a) RR x RR b) Rr x Rr c) RR x rr 10. When two different alleles occur together, such as Rr, the one that is expressed is a) dominant b) recessive

11. What is the diagram shown below called? What does this letter actually represent?

Check for understanding 1. A one-eyed purple people eater is crossed with a two eyed purple people eater. All of their offspring have two eyes. Which trait is dominant?

2. If you use the letter E for this gene. What is the genotype of the offspring if the parents were EE x ee EE = two eyes 3. If you crossed the offspring with each other? How many of the new offspring would you expect to have two eyes? Ee = two eyes ee = one eye

Video Review: Extra Credit Link if video isn’t working: https: //www. youtube. com/watch? v=UTg. Vp. ZYo. HUQ